docs: clone internal repository main branch explicitly

README.md

@@ -62,7 +62,8 @@ python3 ~/.codex/skills/.system/skill-installer/scripts/install-skill-from-githu
 ## 从其他私有 Git 服务安装
 
 ```bash
-git clone https://git.yishihui.com/liulidong/data_query_skill.git data-query-skills
+git clone --branch main --single-branch \
+  https://git.yishihui.com/liulidong/data_query_skill.git data-query-skills
 mkdir -p ~/.codex/skills
 cp -R data-query-skills/skills/* ~/.codex/skills/
 ```